Metal Oxide films, such as Niobium Oxide (Nb2O5), have been extensively utilized in various fields of technology. Traditionally these oxides have been applied as resistive films used as high-k materials for insulating layers. For instance, a thin layer of Nb2O5 between two ZrO2 dielectric layers is expected to help significantly reduce leakage current and stabilize the cubic/tetragonal phase of the ZrO2, affording higher k values in the current MIM capacitor of a DRAM. (Alumina, J. Vac. Sci. Technol A 4 (6), 1986 and Microelectronic Engineering 86 (2009) 1789-1795).
Metal Nitride films, such as Niobium Nitride (NbNx wherein x is approximately 1) have been extensively utilized in various fields of technology. Traditionally these nitrides have been applied as hard and decorative coatings but during the past decade they have increasingly been used as diffusion barrier and adhesion/glue layers in microelectronic devices [Applied Surface Science 120 (1997) 199-212]. NbCl5 for instance has been examined as a niobium source for Atomic Layer Epitaxial growth of NbNx, but the process required Zn as a reducing agent [Applied Surface Science 82/83 (1994) 468-474]. NbNx films were also deposited by atomic layer deposition using NbCl5 and NH3. [Thin Solid Films 491 (2005) 235-241]. The chlorine content showed strong temperature dependence as the film deposited at 500° C. was almost chlorine free, while the chlorine content was 8 at. % when the deposition temperature was as low as 250° C. Id. The high melting point of NbCl5 also makes this precursor difficult to use in the vapor deposition process.
Gust et al. disclose the synthesis, structure, and properties of niobium and tantalum imido complexes bearing pyrazolato ligands and their potential use for the growth of tantalum nitride films by CVD. Polyhedron 20 (2001) 805-813.
Elorriaga et al. disclose asymmetric niobium guanidinates as intermediates in the catalytic guanylation of amines (Dalton Transactions, 2013, Vol. 42, Issue 23 pp. 8223-8230).
Tomson et al. disclose the synthesis and reactivity of the cationic Nb and Ta monomethyl complexes [(BDI)MeM(NtBu)][X] (BDI=2,6-iPr2C6H3—N—C(Me)CH—C(Me)-N(2,6-iPr2C6H3); X=MeB(C6F5)3 or B(C6F5)4) (Dalton Transactions 2011 Vol. 40, Issue 30, pp. 7718-7729).
A need remains for developing liquid or low melting point (<50° C. at standard pressure), highly thermally stable, Niobium-containing precursor molecules suitable for vapor phase film deposition with controlled thickness and composition at high temperature.